I'm pretty sure you can step on crap. I once saw it in a French movie.
6 seconds sound clip from the Good Morning, Vietnam movie soundboard.
You can hear this line at 00:47:07 in the Blu-ray version of the movie.
Quote context
[...]
- Uh, look what you did. And goddamn it and stupid and crap.
- That's stupid, you don't call someone crap.
- No, you step on crap. You don't call it to a person.
- You can step on crap. I know you can.
- Yes, but they can be full of shit, he said.
- No, no, you see, you step in shit, you can be full of crap.
- I'm pretty sure you can step on crap. I once saw it in a French movie.
- How can some person look like a shit? It impossible.
- Okay. Let's stop with that. We can stop with the debate on the great caca right now.
- Let's try a very special situation. Something special, okay?
[...]